Origin: Fascia of the Forearm
The interosseous membrane is derived from the fascia of the forearm (fascia antebrachii), which forms a dense protective sleeve around the forearm musculature.
Deep extensions of this fascia give rise to intermuscular septa and the interosseous membrane (membrana interossea antebrachii), which attaches to the interosseous borders of the radius and ulna.
Distally, the antebrachial fascia thickens to form:
- Extensor retinaculum (retinaculum extensorum) — located on the posterior aspect.
- Flexor retinaculum (retinaculum flexorum) — also known as the transverse carpal ligament, which forms the roof of the carpal tunnel.
Structure and Apertures
The structure of the membrane is reinforced by the oblique cord (chorda obliqua).
The membrane contains two primary gaps:
- Proximal aperture.
- Distal aperture.
These openings allow the passage of neurovascular structures between the anterior and posterior compartments.
Topography: Posterior Fascial Compartment of the Forearm
The interosseous membrane contributes significantly to the boundaries of the posterior fascial compartment of the forearm (compartimentum antebrachii posterius).
The walls of this compartment are formed as follows:
- Anterior wall — bones of the forearm (radius and ulna) and the interosseous membrane.
- Posterior wall — deep fascia of the forearm (fascia antebrachii).
- Lateral wall — posterior intermuscular septum of the forearm.
- Medial wall — fusion of the deep fascia with the posterior border of the ulna.
Relationship with Forearm Muscle Groups
The muscles of the forearm (mm. antebrachii) are organized into functional groups:
- Anterior group (flexores, pronatores) — flexors and pronators.
- Posterior group (extensores, supinatores) — extensors and supinators.
- Lateral (radial) group — occupies an intermediate position.
All muscle groups are enclosed by the fascia antebrachii, which sends inward intermuscular septa and the interosseous membrane (membrana interossea antebrachii).
- Brachioradialis muscle (m. brachioradialis) originates from the lateral supracondylar ridge of the humerus and the lateral intermuscular septum, inserting onto the styloid process of the radius. It acts as a forearm flexor and assists in returning the pronated or supinated forearm to a neutral position. It is innervated by the radial nerve (n. radialis, C5–C7) and supplied by the radial and radial collateral arteries (a. radialis, a. collateralis radialis).
- Supinator muscle (m. supinator) originates from the lateral epicondyle of the humerus, radial collateral ligament, annular ligament of the radius (lig. collaterale radiale, lig. anulare radii), and the supinator crest of the ulna. It inserts onto the lateral and anterolateral surfaces of the proximal third of the radius, functioning to supinate the forearm. It is innervated by the deep branch of the radial nerve (C6–C7) and vascularized by the recurrent radial and posterior interosseous arteries (a. recurrens radialis, a. interossea posterior).